Alelopatia de extratos de milheto e crotalária em sementes e plântulas de alface e tomate

Abstract

Allelopathy can be seen as the interference of one being over another, and can be positive or negative. The use of plants to cover the soil has become a trend for soil management and conservation, but some of the plants used can release secondary metabolites that will interfere in the germination and development of cultivated plants. Thus, the present work aimed to verify if aqueous extracts of millet and crotalaria interfere in the germination and growth of lettuce and tomato seedlings. The design used was entirely randomized using roots, leaves and flowers of each plant separately in a 2x4 factorial scheme (cover plants x concentrations) with 4 repetitions in each species separately. The lettuce seeds were from the Lisa cultivar and the tomato seeds were from the Rio Grande cultivar. The seeds were placed in gerboxes and soaked with 10 ml of the aqueous extract. The variables analyzed were: germination percentage, presence of abnormal seedlings, length of the aerial part and seedling roots, and dry mass of the aerial part and seedling roots. The data obtained were submitted to variance analysis, and when it was significant, regression analysis was performed. The extracts of millet and crotalaria flowers at 0, 25%, 50% and 100%, showed difference only in the variables root length and aerial part of the lettuce seedlings from 25% of concentration of the extract; the tomato seeds when receiving flower extracts showed difference only in non germinated seeds, abnormal seedlings and germination speed index in doses from 25% of concentration. In lettuce seeds, the extracts of millet and crotalaria leaves, when tested in concentrations of 0, 25%, 50% and 100%, showed a difference starting from 25% in the germination, abnormal seedlings, germination speed index, root length and dry mass of roots and aerial part variables. In tomato, there was a statistical difference in germination, non-germinated seeds, abnormal seedlings, germination speed index, length of the aerial part and roots, besides the dry mass of roots and aerial part, all starting from a 25% concentration. The extracts of Milheto campeiro and Crotalária breviflora roots interfered in lettuce seeds in the following variables: germination, abnormal seedlings, germination speed index, length of roots and aerial part of the seedlings from 25 or 50% concentration. In tomato seeds, there was a significant difference in the variables germination, abnormal seedlings and germination speed index at concentrations above 25%. Thus, we conclude that all extracts preparations caused some interference in seed germination and growth of seedlings of Smooth Lettuce and Tomato Rio Grande.